1. Field of the Invention.
This invention relates in general to a network communications, and more particularly to a knowledge-based connection admission method and apparatus for providing efficient multiplexing of data and speech over AAL2.
2. Description of Related Art.
ATM has been selected as a world standard for broadband ISDN in network communication systems. ATM systems have been implemented on a global basis and developed in a rapid growth. ATM technology is destined to play a major role in both public and private broadband networks. AAL2 is one of the four types of AAL (ATM Adaptive Layer) protocols which have been recommended by CCITT (now ITU-T), namely AAL1, AAL2, AAL3/4 and AAL5. In general, the layer services provided by AAL1 are constant bit rate (CBR) services which require information to be transferred between source and destination at a constant bit rate. AAL2 offers a transfer of information with a variable bit rate. In addition, timing information is transferred between source and destination. Since the source is generating a variable bit rate, it is possible that cells are not completely filled and that filling level varies from cell to cell. AAL3/4 is used for transfer of data which is sensitive to loss, but not sensitive to delay. The AAL3/4 protocol may be used for connection oriented as well as for connectionless data communication. AAL3/4 itself does not perform all functions required by a connectionless service, since functions like routing and network addressing are performed on the network layer. AAL5 is designed to offer a service with less overhead and better error detection below the common part of the convergence sublayer (CPCS).
The AAL2 signaling protocol describes methods by which a switched AAL2 connection can be established between two AAL2 end users across a network that consists of both ATM and AAL2 switches. The important function of AAL2 signaling protocol is to establish an AAL2 connection between two AAL2 end points on a concatenation of ATM Virtual Channel Connections (VCCs) that are either on demand (SVC) or semi-permanent (PVC). Some the basic requirements of AAL2 signaling protocol include the ability to establish an AAL2 connection between AAL2 end systems that support AESA formats, the ability to support hop-by-hop routing mechanism between AAL2 end systems, the ability to indicate any failures to corresponding management entity, and the ability to setup AAL2 connections with different Quality-of-Service (QoS) requirements. In AAL2, packets (minicells) from many users are assembled into a single ATM cell and transmitted on the same ATM connection. In addition, packets are allowed to straddle across ATM cell boundary to maximize the bandwidth utilization.
The success of ATM in wireline network has given impetus to the wireless network operators to adopt ATM for efficient use of network resources and able to support growing demands for different services. With AAL2, low bit rate and delay sensitive applications, such as mobile telephony, share a common ATM VCC thus increasing statistical multiplexing efficiency. Bandwidth efficiency, due to AAL2 for delay sensitive speech traffic, has been confirmed by simulation studies and commercial products available today.
The AAL2 standard consists of Common Part Sublayer (CPS) and Segmentation and Reassembly Service Specific Convergence Sublayer (SAR-SSCS ). The CPS standard describes the procedures involved in multiplexing packets from different users on a single ATM VCC and the SAR-SSCS standard specifies ways to carry packets that are larger than 64 bytes in AAL2.
The procedure involved in transmitting data over AAL2 is similar to AAL5. A data packet received from a user is added 8 byte Service Specific Transmission Error Detection Sublayer (SSTED) trailer similar to AAL5 trailer. Even though, SAR-SSCS specification describes three different ways to transmit a data packet, the SSTED trailer is added to obtain similar services offered by AAL5. The main difference between AAL5 and AAL2 is the padding, which is not needed in AAL2. If the size of a data packet is larger than 64 bytes then it is segmented into multiple of 64 bytes. Each segment is converted into CPS-Packet with a 3 byte header and passed to the CPS layer for AAL2 multiplexing. The CPS layer assemble these minicells in ATM cells and transmit them to remote AAL2 peer entity. The maximum size of a data packet is limited to 65535 octets in SAR-SSCS.
Recently, there has been considerable interest in multiplexing best effort data traffic along with speech to achieve the maximum bandwidth efficiency in the output ATM link. However, with current multiplexing method and apparatus, speech and best effort data traffic are separated, with one VCC handling one type of traffic and a second VCC utilizing another AAL standard for handling another type of traffic, i.e., different Quality of Service. If there are not ATM cells to transmit from the first VCC, then ATM cells from the second VCC will be transmitted automatically. This is a standard procedure implemented in ATM switches that are available today.
Nevertheless, AAL2 introduces a situation where the leftover bandwidth in one of the VCCs may not be used for any best effort data traffic. This may lead to ATM cells in one of the VCCs being partially filled resulting in in-efficient bandwidth utilization. Thus, potentially available bandwidth can not be used by any other traffic that passes through the ATM switch.
It can be seen that there is a need for a connection admission method and apparatus that uses knowledge-based techniques to decide when and what type of data traffic will be multiplexed with speech traffic in ATM Adaptation Layer 2 (AAL2) environment.
It can also be seen that there is a need for a connection admission method and apparatus that supports low bit rate and delay sensitive applications such as mobile telephony in an ATM environment.
It can also be seen that there is a need for a connection admission method and apparatus that maximizes the use of available bandwidth.
To overcome the limitations in the prior art described above, and to overcome other limitations that will become apparent upon reading and understanding the present specification, the present invention discloses a knowledge-based connection admission method and apparatus for providing efficient multiplexing of data and speech over AAL2.
The present invention solves the above-described problems by using a knowledge-based technique to decide when and what type of data traffic will be multiplexed with speech traffic in ATM Adaptation Layer 2 (AAL2) environment. The knowledge-based connection technique supports low bit rate and delay sensitive applications such as mobile telephony in an ATM environment by maximizing the use of available bandwidth.
A method in accordance with the principles of the present invention includes monitoring ATM cells for a AAL2 connection, determining whether the ATM cells contain unused bytes and multiplexing data traffic with speech traffic on the AAL2 connection when the data meets a predetermined set of requirements.
Other embodiments of a system in accordance with the principles of the invention may include alternative or optional additional aspects. One such aspect of the present invention is that the multiplexing further includes determining whether the data traffic requires a bandwidth that exceeds a bandwidth provided by the unused bytes and multiplexing the data traffic with the speech traffic when the bandwidth required by the data traffic does not exceeds the bandwidth provided by the unused bytes.
Another aspect of the present invention is that the multiplexing further includes determining whether the data traffic requires a bandwidth that exceeds a bandwidth provided by the unused bytes and preventing the multiplexing of the data traffic with the speech traffic when the bandwidth required by the data traffic exceeds the bandwidth provided by the unused bytes.
Another aspect of the present invention is that the unused bytes represent silence periods during speech traffic.
Another aspect of the present invention is that the multiplexing further includes gathering system observations, processing the system observations with prior knowledge about the system, based upon the processing, determining whether the data traffic is suitable for multiplexing with speech traffic and multiplexing the data and speech traffic when the data traffic is determined to be suitable for multiplexing-with speech traffic.
Another aspect of the present invention is that the determining further includes determining whether a number of users providing speech traffic are fewer than a predetermine number and unused bytes exist in ATM cells of the speech traffic of the users, calculating the percentage of unused bandwidth of the speech traffic and multiplexing an amount of data traffic with the speech traffic in proportion to the unused bandwidth of the speech traffic.
Another aspect of the present invention is that the multiplexing an amount of data traffic further includes determining whether the unused bandwidth is greater than the bandwidth requested by a data connection and admitting the data connection when the unused bandwidth is greater than the bandwidth requested by the data connection.
Another aspect of the present invention is that the multiplexing an amount of data traffic further includes determining whether the unused bandwidth is greater than the bandwidth requested by a data connection and rejecting the data connection when the unused bandwidth is not greater than the bandwidth requested by the data connection.
Another aspect of the present invention is that the method further including updating the prior knowledge about the system after determining whether the data traffic is suitable for multiplexing with speech traffic.
Another aspect of the present invention is that the updating the prior knowledge further includes asserting the number of speech users when the connection from the speech users is accepted, asserting the delay guarantee of the speech users when a change in the delay guarantee of the speech users occurs, asserting the resource allocated for speech users when there is a change in resource allocation for speech users, and asserting the traffic pattern of the speech users when there is a change in the traffic pattern of speech users.
These and various other advantages and features of novelty which characterize the invention are pointed out with particularity in the claims annexed hereto and form a part hereof. However, for a better understanding of the invention, its advantages, and the objects obtained by its use, reference should be made to the drawings which form a further part hereof, and to accompanying descriptive matter, in which there are illustrated and described specific examples of an apparatus in accordance with the invention.